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22 Nov 1999

Volume 75, Issue 21, pp. 3243-3419

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Field emission study of gated GaN and Al0.1Ga0.9N/GaN pyramidal field emitter arrays

T. Kozawa, T. Ohwaki, Y. Taga, and N. Sawaki

Appl. Phys. Lett. 75, 3330 (1999); http://dx.doi.org/10.1063/1.125341 (3 pages) | Cited 16 times

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A self-aligned process has been proposed for fabrications of gated GaN and Al0.1Ga0.9N/GaN pyramidal field emitters with a small and precise distance between the gate electrode and the emitter tip. The sharp pyramidal emitters were obtained by a selective area growth technique. SiO2 and polyimide were used as the insulating layers between the emitters and the gate electrode. The gate-tip spacing and the tip protrusion through the gate openings were precisely controlled by adjusting the thickness of the SiO2 and polyimide layers. The turn-on voltage was reduced by narrowing the gate-tip spacing and by using Al0.1Ga0.9N/GaN emitter instead of GaN; the low onset gate voltage of 42 V was obtained for a gate-tip spacing of 0.4 μm. © 1999 American Institute of Physics.
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85.45.Db Field emitters and arrays, cold electron emitters

Room-temperature blue luminescence of thermally oxidized Si1−x−yGexCy thin films on Si (100) substrates

Xuemei Cheng, Youdou Zheng, Xiabing Liu, Lan Zang, Zhiyun Lo, Shunming Zhu, Ping Han, and Ruolian Jiang

Appl. Phys. Lett. 75, 3333 (1999); http://dx.doi.org/10.1063/1.125342 (3 pages) | Cited 1 time

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We measured at room temperature the photoluminescence spectra of the thermally oxidized Si1−x−yGexCy thin films which were grown on silicon substrates by plasma-enhanced chemical vapor deposition and then wet oxidized at 1100 °C for 20 min. The photoluminescence band with a peak at ∼393 nm under the exciting radiation of λ = 241 nm was observed. Possible mechanism of this photoluminescence is discussed. © 1999 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.65.Mq Oxidation
78.66.Li Other semiconductors
81.05.Hd Other semiconductors

Ultrafast carrier trapping in Be-doped low-temperature-grown GaAs

A. Krotkus, K. Bertulis, L. Dapkus, U. Olin, and S. Marcinkevičius

Appl. Phys. Lett. 75, 3336 (1999); http://dx.doi.org/10.1063/1.125343 (3 pages) | Cited 18 times

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Time-resolved photoluminescence is used to study low-temperature-grown (LTG) GaAs with Be doping. It is observed that the carrier trapping time in the as-grown LTG GaAs increases with Be doping. Similar effect is observed also in the annealed samples doped with less than 3×1019 cm−3 of Be. At higher doping levels, the trapping time in these samples is abruptly reduced to below 100 fs. This behavior is attributed to changes in As antisite density and the compensation effect of Be. © 1999 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Spatially resolved luminescence investigation of AlGaAs/GaAs single quantum wires modified by selective implantation and annealing

Xingquan Liu, Wei Lu, Zhi Feng Li, Yi Dong Chen, S. C. Shen, Y. Fu, M. Willander, Hark Hoe Tan, S. Yuan, C. Jagadish, J. Zou, and D. J. H. Cockayne

Appl. Phys. Lett. 75, 3339 (1999); http://dx.doi.org/10.1063/1.125344 (3 pages) | Cited 8 times

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Single Al0.5Ga0.5As/GaAs V-groove quantum wires (QWR) modified by selective implantation and rapid thermally annealing were investigated by spatially resolved microphotoluminescence (micro-PL). The PL from the necking region was clearly observed at room temperature. Optical properties of QWR and the adjacent quantum well structures were strongly degraded by the implantation. The recovery properties of the PL signals from all the structures were dependent on the implantation dose. A critical dose of 1×1013 cm−2 was found for the selective implantation, over which the PL from the necking region could not be recovered. Also the blueshifts of QWR and the necking-region PL peaks were observed for all the annealed samples. This blueshift is caused by the interface intermixing, which is very useful to increase the confinement of carriers in QWR region for optoelectronic device applications. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.35.Fx Diffusion; interface formation

Current transients in almost-ideal Czochralski silicon p–n junction diodes

A. Poyai, E. Simoen, and C. Claeys

Appl. Phys. Lett. 75, 3342 (1999); http://dx.doi.org/10.1063/1.125345 (3 pages) | Cited 2 times

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The nature of the reverse current transients in large-area nearly ideal p–n junction diodes fabricated on Czochralski silicon substrates is investigated. It is shown that they can be generated by an electrical or optical excitation pulse. A typical nonexponential behavior with time is observed. The best fit is found for a power-law function. The impact of the reverse bias and the temperature on the prefactor and on the exponent will be presented. From the observations, it is concluded that the capture of electrons is a necessary step for the generation of the transients. A discussion of the possible nature of the underlying defects is given, and the implications for practical current–voltage characterization will be discussed. © 1999 American Institute of Physics.
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85.30.Kk Junction diodes
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Ohmic contacts to p-type ZnSe using a ZnSe/BeTe superlattice

F. Vigué, P. Brunet, P. Lorenzini, E. Tournié, and J. P. Faurie

Appl. Phys. Lett. 75, 3345 (1999); http://dx.doi.org/10.1063/1.125346 (3 pages) | Cited 8 times

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Various configurations of pseudograded BeTe/ZnSe superlattices have been investigated to form a nonalloyed contact onto nitrogen-doped p-type ZnSe layers. Best results were obtained by using a fully N-doped superlattice with a 20-ML-thick pseudoperiod and with the thickness of individual layers in the pseudoperiod varying by 1 ML steps. A specific contact resistance of 6×10−2 Ω cm2 has been measured for a ZnSe p-type doping level of 2×1017 cm−3. Truly perfect ohmic contact is obtained. © 1999 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
81.05.Dz II-VI semiconductors
73.40.Cg Contact resistance, contact potential
73.61.Ga II-VI semiconductors

Photoelectrical properties of a ferroelectric liquid crystalline photoconductor

Kyoko Kogo, Hiroki Maeda, Hiroaki Kato, Masahiro Funahashi, and Jun-ichi Hanna

Appl. Phys. Lett. 75, 3348 (1999); http://dx.doi.org/10.1063/1.125347 (3 pages) | Cited 4 times

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An organic ferroelectric photoconductor, 2-[(S)-4-(6-methylheptyloxy)phenyl]-6-decylnaphthalene, was prepared and its photoconductive and ferroelectric behaviors were characterized by steady-state and transient electrical measurements. This material exhibited fast carrier transport with an ambipolar mobility of 2.6×10−4 cm2/V s, independent of temperature and electric field. Under a polarized microscope, a fast switching with memory effect was observed visually and the spontaneous polarization was evaluated to be 0.6 nC/cm2 in chiral smectic C phase. © 1999 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena
72.30.+q High-frequency effects; plasma effects
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Le Polymers; organic compounds (including organic semiconductors)

Very low densities of localized states at the Fermi level in hydrogenated polymorphous silicon from capacitance and space-charge-limited current measurements

J. P. Kleider, C. Longeaud, M. Gauthier, M. Meaudre, R. Meaudre, R. Butté, S. Vignoli, and P. Roca i Cabarrocas

Appl. Phys. Lett. 75, 3351 (1999); http://dx.doi.org/10.1063/1.125348 (3 pages) | Cited 23 times

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The density of states at the Fermi level N(EF) has been measured on hydrogenated polymorphous (pm-Si:H) silicon samples using both capacitance measurements on Schottky barriers and space-charge-limited current measurements on n+/i/n+ structures. From both techniques, N(EF) values of 7–8×1014 cm−3 eV−1 have been obtained, which is significantly lower than reported in the literature for hydrogenated amorphous silicon (a-Si:H). Such values demonstrate that pm-Si:H is a very low defect density material which should be able to replace a-Si:H in the field of applications like photovoltaics. © 1999 American Institute of Physics.
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71.20.Mq Elemental semiconductors
71.55.Cn Elemental semiconductors
72.20.Ht High-field and nonlinear effects
73.30.+y Surface double layers, Schottky barriers, and work functions

Effect of initial surface reconstruction on the GaS/GaAs(001) interface

R. I. Pelzel, B. Z. Nosho, W. V. Shoenfeld, T. Lundstrom, P. M. Petroff, and W. H. Weinberg

Appl. Phys. Lett. 75, 3354 (1999); http://dx.doi.org/10.1063/1.125349 (3 pages) | Cited 2 times

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We have used photoluminescence of a GaAs/Al0.3Ga0.7As near-surface quantum well structure to study the quality of the interface between GaAs and GaS deposited in ultrahigh vacuum (UHV) using [(tBu)GaS]4. In addition to the luminescence of the near-surface and the deep/reference quantum wells, luminescence was observed for the GaAs cap following the deposition of 100 Å of GaS. This additional feature demonstrates the high quality GaS/GaAs interface achievable through the UHV deposition of this precursor. The ratios of the integrated luminescence intensity of both the GaAs cap and the near-surface GaAs quantum well to the deep/reference quantum well indicate that there are fewer GaS/GaAs interface states for deposition on the Ga-rich GaAs(001)-(4×2)/(2×6) surface compared to deposition on the As-rich GaAs(001)-(2×4) surface. Furthermore, GaS passivated samples exposed to ambient conditions for eight months exhibit no luminescence degradation for the near-surface quantum well confirming that these films provide adequate passivation longevity. © 1999 American Institute of Physics.
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68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.65.Rv Passivation
81.05.Ea III-V semiconductors

Characterization of hydrogen-terminated Si(111) surfaces by sum-frequency surface vibrational spectroscopy

M. Y. Mao, P. B. Miranda, D. S. Kim, and Y. R. Shen

Appl. Phys. Lett. 75, 3357 (1999); http://dx.doi.org/10.1063/1.125350 (3 pages) | Cited 6 times

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Sum-frequency surface vibrational spectroscopy was used to characterize H-terminated Si(111) surfaces prepared by different methods. It was found that flash heating of a sample to 1500 K followed by H2 dosing at 900 K yields a surface as good in quality as a wet chemically treated surface. Both surfaces are far superior than that prepared by atomic H adsorption. © 1999 American Institute of Physics.
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68.35.Ja Surface and interface dynamics and vibrations
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.30.Am Elemental semiconductors and insulators
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.65.Rv Passivation
81.05.Cy Elemental semiconductors

SiO2/6H-SiC(0001)3×3 initial interface formation by Si overlayer oxidation

F. Amy, P. Soukiassian, Y.-K. Hwu, and C. Brylinski

Appl. Phys. Lett. 75, 3360 (1999); http://dx.doi.org/10.1063/1.125351 (3 pages) | Cited 29 times

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We investigate the initial oxidation and SiO2/6H-SiC interface formation by core level photoemission spectroscopy using synchrotron radiation. The results indicate that the direct oxidation of the 6H–SiC(0001)3×3 surface leads to SiO2 formation at low temperatures (500 °C) with a nonabrupt interface having significant amounts of mixed (Si–O–C) and intermediate (Si3+,Si2+,Si+) oxidation products. In contrast, C-free and a much more abrupt SiO2/6H-SiC(0001) interface formation is achieved when predeposited Si overlayer is thermally oxidized at low oxygen exposures and low temperatures (500 °C). © 1999 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Hd Other semiconductors
73.20.At Surface states, band structure, electron density of states
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
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